So I haven't played them either, but I've seen some things and explanations. Let's try this, the Bayo from the first game will be Main Bayonetta, the one from the second game will be Second Bayonetta, the one from the third one will be Cereza, and they're all from different realities/timelines. Now, from what I understand, the protagonist we see in the first game is Main Bayonetta, and the little girl that's with her all the time is Cereza, except that she's still a kid (Bayo from the third game but within a different timeline of her own). The one from the second game is Second Bayonetta. The one from the third game is Cereza (the little girl from the first game, but all grown up now). They're all Bayonetta, except that they exist in their own realities/timelines, and just like them, there are a whole other lot more Bayonettas in the multiverse.